A graphic representation may include a digital photograph (i.e., image captured digitally) or digitized photograph (i.e., image captured as a film-based photograph that is later digitally scanned), both of which will be referred to herein as a digital image. The digital image is formed from a large number of individual picture elements (pixels), with each pixel representing a finely discrete, spatially identifiable portion of the digital image as a single color or shade of gray.
The spatially identifiable portion of the digital image represented by each pixel is usually very small, such that individual pixels ordinarily cannot be seen by the unaided eye. The pixels are arranged in a grid having rows and columns. When the pixels making up the digital image are viewed by a human at a comfortable distance (e.g., arm's length of about 2-3 feet), typically without magnification, the individual pixels are perceived by the eye and mind as blending to form a continuous, non-discretized image. The digital image is finely-discretized (i.e., a finely-discretized digital image), and if in color typically will use a color palette having a large number of possible colors for each pixel, such as 16 million colors representable by a 24-bit color word. The digital image, if in black and white, is also finely-discretized and may include a somewhat smaller but still large number of shades of gray, such as 256 shades (8-bit) or 65,536 shades (16-bit). A difference between adjacent shades or colors is indiscernible or nearly indiscernible to the naked eye.
A graphic representation may also include images not made from photographs, for instance a tessellation, a painting, a collection of geometric shapes, artistic design prints, etc. Non-photographic graphic representations may be scanned or photographed and then further treated as if they are a digital image.
When the finely-discretized digital image is reproduced on a physical medium, such as by printing on paper, the individual pixels are formed by placing a small amount of ink or other colorant (e.g., toner) at a location that corresponds to the location of each pixel in the digital image. The resulting image is a substantially two-dimensional image. The thickness of the image, formed by the thickness of the ink or colorant, is negligible. This produces a flat image. The colorant often covers the entire area of the image (usually a rectangular shape), especially when printing a digital photograph, even when the colorant is the same color as a non-white physical medium (e.g., colored paper stock) it may be placed upon.